We have moved all aspects of this umbrella project forward during 2013. We discovered that C-terminal domains within ATPase proteins that dock against the proteasome's core particle undergo dynamic exchange between an expected 4-helix bundle and a partially unfolded state. We provided evidence that this exchange is important for interactions with chaperones involved in proteasome assembly. In unpublished work, we have moved forward the resolution of the 3D structures for multiple protein complexes, including a new ubiquitin binding motif.